[Illustration: FIG. 236.--A voltmeter.]
The unit of electromotive force is called the _volt_. The voltage of a
dry cell is approximately 1.5 volts, and the voltage of a voltaic cell
and of a gravity cell is approximately 1 volt.
316. Current, Voltage, Resistance. We learned in Section 287 that
the strength of a current increases when the electromotive force
increases, and diminishes when the electromotive force diminishes.
Later, in Section 288, we learned that the strength of the current
decreases as the resistance in circuit increases.
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